Abstract
Abstract:
A measurement of the production of three isolated photons in proton–proton collisions at a
centre-of-mass energy √s = 8 TeV is reported. The results are based on an integrated
luminosity of 20.2 fb−1collected with the ATLAS detector at the LHC. The differential cross
sections are measured as functions of the transverse energy of each photon, the difference in
azimuthal angle and in pseudorapidity between pairs of photons, the invariant mass of pairs of
photons, and the invariant mass of the triphoton system. A measurement of the inclusive fiducial
cross section is also reported. Next-to-leading-order perturbative QCD predictions are compared to
the cross-section measurements. The predictions underestimate the measurement of the inclusive
fiducial cross section and the differential measurements at low photon transverse energies and
invariant masses. They provide adequate descriptions of the measurements at high values of the
photon transverse energies, invariant mass of pairs of photons, and invariant mass of the triphoton
system.